Timber Calculator

How the timber calculator works

Calculates board feet or linear metres of timber by section and count. The calculator takes your dimensions and supplier rates, applies a standard UK trade formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.

Typical UK timber and framing wastage

Timber wastage runs 5–10% on straight cuts, 10–15% for angled or notched framing. Order at lengths that minimise splicing — a 4.8 m joist often orders cheaper than two 2.4 m. Our defaults reflect common UK trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.

What this tool does not do

It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm Building Regulations compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building control officer.

On-site considerations for timber

Check grading stamps (C16, C24) on every length — structural timber must be graded to BS EN 14081. Moisture content should be below 20% for internal use; above this, shrinkage and movement are significant.

Building Regulations and compliance

Structural framing is subject to Approved Document A. Span tables in TRADA guidance are indicative only — your building control officer will want calculations for anything unusual. When in doubt, a pre-application enquiry to the local authority can give early clarity, which tends to be less costly than retrospective correction.

Before you order

Buy treated timber (UC3 for exposed, UC4 for ground contact) even for internal joists near wet areas. The premium is small next to the labour cost of a rebuild. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.

Adjusting the defaults

Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.

Using this timber calculator alongside other BuildMetricLab tools

This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labour-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.